with a grain of salt

With reservations or the understanding that some rumor or piece of information may not be completely true or accurate. Possibly a reference to an ancient Roman antidote to poison that included or consisted of a grain of salt. Kevin said that you can get into the club for free if you wear red, but I always take what he says with a grain of salt. Read whatever that paper publishes with a grain of salt—it's really just a trashy tabloid.

with a pinch of salt

With reservations or the understanding that some rumor or piece of information may not be completely true or accurate. Possibly a reference to an ancient Roman antidote to poison that included or consisted of a grain of salt. Kevin said that you can get into the club for free if you wear red, but I always take what he says with a pinch of salt. Read whatever that paper publishes with a pinch of salt—it's really just a trashy tabloid.

with a grain/pinch of salt, (to take)

Not to be believed entirely; to be viewed with skepticism. This term comes from the Latin cum grano salis, which appeared in Pliny’s account of Pompey’s discovery of an antidote against poison that was to be taken with a grain of salt added (Naturalis Historia, ca. a.d. 77). The term was quickly adopted by English writers, among them John Trapp, whose Commentary on Revelations (1647) stated, “This is to be taken with a grain of salt.”